ZnO Additive Boosts Charging Speed and Cycling Stability of Electrolytic Zn–Mn Batteries

Highlights Low pH value of electrolyte suppresses the charge capabilities of electrolytic Zn–Mn batteries. Unique solid phase alkaline properties of zinc sulfate hydroxide hydrate endow the electrolytic Zn–Mn batteries with greatly enhanced charge capabilities. The highly active Zn2Mn3O8·H2O nanorods array deposited during the charge process improve the discharge efficiency and stability of electrolytic Zn–Mn batteries. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-023-01296-y.

To prepare the ZnO gel-like electrolyte, 0.5, 1, 1.5, 2 and 2.5 grams of ZnO were added to a 10 mL solution consisting of 1 M ZnSO4 and 2 M MnSO4.The mixture was then stirred for 10 minutes to obtain the ZnO gel-like electrolyte.If not specified otherwise, the concentration of ZnO in the ZnO-gel-like electrolyte is 0.2 g mL.

S1.2 Battery Assembly
In our research, we utilized a transparent glass cell to create a visually transparent electrolytic Zn-Mn battery.Carbon nanotubes film served as the cathode substrate, while polished Zn foil (thickness approximately 0.2 mm) and 1 M ZnSO4 + 2 M MnSO4 aqueous solution were used as the anode and electrolyte, respectively.We added 0.66% (w/w) bromocresol green (dissolved in 1% (w/w) ethanol) to the electrolyte to investigate the pH change in situ.The bromocresol green undergoes a color change between pH 3.8 and 5.5, and the pH value of the standard electrolyte (1 M ZnSO4 + 2 M MnSO4) is 4.6.
To perform the gas production measurements on the electrolytic Zn-Mn batteries, the soft packed battery with a gas guide tube was assembled.The cathode consisted of a CNTs film with an area of 12 cm -2 , while the anode was made of Zn metal foil with the same area.The Whatman fiberglass was used as the separator between the two electrodes.The CNTs film was firmly pressed onto the steel foil on the cathode side.

Nano-Micro Letters S2/S28
Finally, we wrapped the battery with polyvinyl chloride film and sealed it using hot melt adhesive to ensure its integrity.
To perform electrochemical measurements on the electrolytic Zn-Mn batteries, we employed CR2032 coin-type cells.We used glass fiber (Whatman, GF/D) as the separator, carbon nanotubes films (thickness approximately 0.06 mm, area 1.13 cm -2 , weight 1.5 mg) as the cathode substrate, and polished Zn foil (thickness approximately 0.2 mm, area 1.33 cm -2 ) as the anode electrode.We assembled different CR2032 cointype electrolytic Zn-Mn batteries with varying electrolytes to conduct different electrolyte performance tests.The volume of electrolyte used in each CR2032 cell was 100 μL.
The square battery utilized Glass fiber as the separator (Whatman, GF/D), with carbon nanotubes films (thickness ~ 0.06 mm, 20 cm -2 ) serving as the cathode substrate and polished Zn foil (thickness ~ 0.05 mm, 20 cm -2 ) acting as the anode electrode.A titanium foil was employed as the current collector, and it leads out the tabs.To serve as the electrolyte, a mixture of 1 M ZnSO4 + 2 M MnSO4, and 0.25 g mL -1 ZnO was utilized.In assembling the pouch shell battery, four slices of CNT cathode were stacked with five slices of Zn metal anode in a forked laminated layout.
The two pouch cells were then assembled into a square shell battery.For the monolithic pouch battery, glass fiber was used as the separator (Whatman, GF/D), with carbon nanotubes membrane (thickness ~ 0.06 mm, 10 cm -2 ) serving as the cathode electrode while zinc sheet (thickness ~ 0.2 mm, 10 cm -2 ) was used as the anode electrode.The pouch battery was sealed, and during charging, N2 was used as the carrier gas to evaluate the generation of gas.

S1.3 Electrochemical Measurements
The chronoamperometric charge and galvanostatic discharge test of the assembled batteries were carried out on the LAND CT2001 test system (Wuhan LAND electronics Co., Ltd, China).Cyclic voltammetry (CV) tests were performed on the CHI760e electrochemical workstation (Chenhua Instrument Company, Shanghai, China).In this study, the test methods of constant voltage charging and constant current discharge were adopted.The voltages in the test are all voltages relative to vs Zn/Zn 2+ .

S1.4 Material Characterization
The phase structure of the electrode materials was determined using X-ray diffraction (XRD), specifically the Shimadzu-7000 model.For observation of morphology, microstructure, and composition, field emission scanning electron microscopy (FESEM) equipped with an energy dispersive spectrometer (EDS) was utilized, specifically the JSM-7800F model.The Raman spectra of the samples were recorded using the LabRAM HR Evolution (Horiba) with a laser excitation at 532 nm.To investigate the surface chemical composition and valence state, X-ray photoelectron spectroscopy (XPS) with the Escalab 250xi model was used.Before testing, all electrodes were washed with deionized water to remove any residual electrolyte.The Mn K-edge X-ray absorption spectra were conducted in fluorescence mode at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility, China, operating at 3.5 GeV with maximum injection currents of 230 mA.To reduce the harmonic component of the monochrome beam, a double-crystal monochromator equipped with a Si (111) crystal was used to monochromatize the synchrotron beam.Reference samples, specifically Mn3O4 standard and MnO2 standard, were used in the experiment.To detect the types of gases produced during battery cycling, meteorological mass spectrometers (GSD320 Omnistar) were utilized with N2 as the carrier gas.The Optima 8000 model of the inductively coupled plasma optical emission spectrometer (ICP-OES) was applied to measure the mass fraction of residual iron catalysts in carbon nanotubes membranes.

S1.5 Methods of Drawing the Pourbaix Diagram
The Pourbaix diagram in the Fig. 2A is get from an Open-Source calculation system of THE MATERIALS PROJECT (https://next-gen.materialsproject.org/).THE MATERIALS PROJECT is a multi-institution, multi-national effort to compute the properties of all inorganic materials and provide the data and associated analysis algorithms for every materials researcher free of charge.In this system, the Pourbaix Diagram can be obtained by inputting the composition of the electrolyte.

S1.6 ZHS Assisted Mn 2+ Deposition-dissolution Reaction
Charge Process: Discharge process: During the deposition process of ZSH, the Zn (H2O)6 2+ first deprotonation step to the intermediate amphoteric [Zn(H2O)5(OH)] + , and then further lead to neutral double hydroxide Zn(H2O)4(OH)2 species.The presence of co-precipitated SO4 2-can slowly convert into the crystalline of Zn(H2O)4(OH)2 to form Zn4SO4(OH)64H2O (Fig. S5) [S1].Thus, in order to better query the standard equilibrium constant, the Equation S6 was equivalently substituted, and shown in as follow: Given that the K θ sp of Zn(OH)2 is 1 × 10 -17 , the C(Zn 2+ ) is 1M.Thus, the start deposition pH of Zn4SO4(OH)64H2O is around 5.5 in 1M ZnSO4.At the same time, according the references [S2, S3], the starting pH of ZnO dissolution reaction is also around 5.5.Thus, when ZnO is added to the solution of 1M ZnSO4 + 2 M MnSO4 (pH is around 4.6), the Eqs.S5 and S6 is occurs rapidly until all the ZnO is consumed.Table S1 The ionic conductivity of different electrolyte electrolyte ionic conductivity (mS cm -1 )  We collected the linear sweep voltammetry curves to analysis the HER and OER property during the first charge process (Fig. S6).Obviously, after introducing the Nano-Micro Letters S7/S28 ZnO electrolyte addition, the HER and OER were suppressed.Specifically, the OER reaction current density is decreased, the HER overpotential is increased and current density is decreased.

S2 Supplementary Figures and Tables
To further investigate the OER and HER reaction during the cycling, the gas volume produced from the electrolytic Zn-Mn batteries with different electrolyte during the cycling were record.As shown in the Fig. S7A, a soft packed battery with a gas guide tube was prepared, the area of CNTs film cathode is 12 cm -2 , the Zn metal foil is anode and Whatman fiberglass is the separate.The gas volume measuring device is shown in the Fig. S7B.To ensure there is no residual gas within the soft packed battery, a fixture was used to secure the soft pack battery.When using ZnO gel-like electrolyte, the max gas produce volume of soft packed electrolytic Zn-Mn batteries is only 0.91 cm -3 after 100 cycling (chronoamperometric charge of 2.0 V vs. Zn/Zn 2+ to 1.5 mAh cm -2 , discharge to 0.8 V vs. Zn/Zn 2+ with 1 mA cm -2 ).Under the same charge-discharge conditions, when without ZnO electrolyte additive, the gas produce volume is continually increased, and reach 14.7 cm -3 at 100 th cycle.Obviously, the ZnO gel-like electrolyte greatly suppresses the gas generation in the electrolytic Zn-Mn batteries during the cycling.Fig. S13 The cross-section view SEM images of the CNTs cathode during the charge process Fig. S14 (A-C) The SEM images of cathode surface during the discharge process.(D-F) The SEM images of cathode cross-section during the discharge process.(Chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ to 1.5 mAh cm -2 and discharge at 1 mA cm -2 ) Fig. S15 The SEM-Energy Dispersive Spectrometer (EDS) mapping of CNTs cathode at discharge state of 0.8 V vs. Zn/Zn 2+ .(Chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ to 1.5 mAh cm -2 and discharge at 1 mA cm -2 ) Nano-Micro Letters S11/S28 A schematic diagram (Fig. S11) was presented to illustrating the evolution process of phase and structure on the cathode surface during the charge-discharge process.The more detail about the morphology evolution of cathode during the charge-discharge process was collected and shown in the Figs.S12-S15.
As shown in the Fig. S11B, due to the presence of ZSH in the electrolyte, the Zn2Mn3O8‧H2O nanorods were deposited on the electrode surface during the charge process.The reaction mechanism can be written as follows: The growth process of Zn2Mn3O8•H2O nanorods was shown in the Fig. S13.With the increased charge capacity, the length of Zn2Mn3O8•H2O nanorods continuously grows, eventually reaching 10.08 μm when it attains 0.8 mAh cm -2 .
As illustrated in Fig. S11C, during the discharge process, the deposited Zn2Mn3O8‧H2O dissolve slowly through a process of hollowing.The reaction mechanism can be written as follows: The dissolution process of Zn2Mn3O8‧H2O nanorods was shown in the Fig. S14A.When discharge to 1.4 V vs. Zn/Zn 2+ , small downward depressions and wrinkles start to appear at the cross-section of Zn2Mn3O8‧H2O nanorods.And then, these concave Zn2Mn3O8‧H2O nanorods transformed into hollow structure at 1.30 V vs. Zn/Zn 2+ (Fig. S14B).With further discharge, the hollow nanorod structure further collapse and dissolve at 1.25 V vs. Zn/Zn 2+ (Fig. S14C).From the Fig. S14D, it is interesting to find that the thickness of the Zn2Mn3O8‧H2O nanorods layer does not show significant changes before discharging to 1.3V vs. Zn/Zn 2+ , which demonstrated that the main contribution to the capacity before discharge to 1.3 vs. Zn/Zn 2+ comes from the hollowing of the Zn2Mn3O8‧H2O nanorods.
At the discharge state of 1.2 vs. Zn/Zn 2+ , a lot of flakes was deposited on the cathode surface, and eventually occupied the entire surface of the cathode at the 0.8 V vs. Zn/Zn 2+ .According to the XRD patterns (Fig. 3A) and SEM-EDS mapping (Fig. S15), the deposited flakes on the cathode surface is Zn4SO4(OH)6•nH2O (ZSH), and the deposition mechanism can be written as follow: The OH − originate from the dissolution process of Zn2Mn3O8‧H2O.The deposition of ZSH was also illustrated in the Fig. S11D.Figure S16A, B demonstrated that the valence state of Mn on the cathode decreased following discharge, regardless of electrolyte type.Specifically, in ZnO gel-like electrolytes, the average valence of manganese in manganese oxides drops from approximately 4 to 3.5.However, in the conventional aqueous electrolyte, the valence state of manganese hardly changes at 1.3 V vs Zn/Zn 2+ , remaining around 3.
We collected the XAFS of Zn K-edge in this sample (Fig. S16C, D), the presence of Zn 2+ in manganese oxides deposited in conventional aqueous electrolyte and gel-like electrolyte.These indicate that the deposited products are all zinc-manganese oxides, but deposited in the form of ZnαMnOx (Z < 4 for Mn z+ ), and deposited in the form of Zn2Mn3O8 (Z = 4 for Mn z+ ) after full charge in gel-like electrolyte.S0 2 : amplitude reduction factor; N: coordination number; ΔE0: shift in edge energy; R(Å): atomic distance; σ 2 : Debye-Waller factor.The bold numbers were obtained by LCF (weight fraction), reference EXAFS fitting (S0 2 ), or ideal values based on stoichiometry (N), and were fixed during these fitting operations.During the deposition process of Mn 2+ , the deposition overpotential of MnO2 will gradually increase as the Mn 2+ ions on the electrode surface are consumed.In the Fig. 5A, the tested electrolytic Zn-Mn batteries is assembled by using CR2032 coin-type Nano-Micro Letters S15/S28 cell mold, an no additional electrolyte diffusion measures.Thus, the limited diffusion behavior of Mn 2+ will cause the overpotential of the deposition reaction to continuously increase.As shown in the Fig. S19A, the CV peaks at 1.8 V vs. Zn/Zn 2+ is very wide, and the current density is 5.3 mA cm -2 at 2.0 V vs. Zn/Zn 2+ (The max current density is 0.7 mA cm -2 at 1.8 V).Thus, because of the limited diffusion behaviors of Mn 2+ , the charge capacity can be significantly increased with increased charge voltage from 1.9 to 2.0 V vs. Zn/Zn 2+ .
In theory, if the charging voltage is adjusted to 2.1 vs. Zn/Zn 2+ , the higher charge capacity of electrolytic Zn-Mn batteries will be achieved.However, as shown in Fig. S19A, the detrimental OER reactions start to take place in the button cell as the voltage gradually increases to 2.1 V vs. Zn/Zn 2+ .In Fig. S19B, when the chronoamperometric charge voltage is 2.1 V vs. Zn/Zn 2+ , the charge capacity can reach 2.76 mAh cm -2 at the 6 th cycles.However, the charge capacity begins to continuously decrease from the 7 th cycle.Thus, in this works, we set the chronoamperometric charge voltage of the electrolytic Zn-Mn battery is 2.0 V vs. Zn/Zn 2+ .As shown in the Fig. S20, the prepared ZnO gel-like electrolyte with different amount ZnO addition all exhibit a uniformly gel-like appearance (Fig. S20A).By inverting the glass vial (Fig. S20B), we can observe that the liquidity of the electrolyte Nano-Micro Letters S16/S28 tends to decrease as the amount of ZnO increases.
The Fig. S20C, D exhibit the charge capacities during initial 20 cycles of electrolytic Zn-Mn batteries with the different amount of ZnO addition (including 0.1, 0.15 and 0.25 g mL -1 ).Obviously, compare to conventional aqueous electrolyte (Fig. 5A), the prepared ZnO gel-like electrolyte with the ZnO concentration of 0.1, 0.15 and 0.25 g mL -1 all can significantly improve the charging capacity of batteries.Under 30 min chronoamperometric charge voltage of 1.9 V vs. Zn/Zn 2+ and 20 cycles, the charge capacities are 1.43, 1.53 and 1.72 mAh cm -2 in 0.1, and 0.15 and 0.25 g mL -1 respectively.When the charging voltage is increased to 2.0 V vs. Zn/Zn 2+ , the charge capacities is increased to 1.57, 1.95 and 2.05 mAh cm -2 in 0.1, 0.25 and 0.15 g mL -1 respectively.Obviously, the electrolyte with an addition of 2 g mL -1 of ZnO exhibits superior ability in enhancing battery charging performance (1.74 and 2.48 mAh cm -2 under chronoamperometric charge voltage of 1.9 and 2.0 V vs Zn/Zn 2+ ) than other ZnO concentration, which may be attributed to the equilibrium between the free water and the amount of zinc oxide added in the electrolyte Fig. S21.Rate performance of the electrolytic Zn-Mn button batteries in (A) ZnO gellike electrolyte and (B) conventional aqueous electrolyte Figure S21 demonstrated that the use of ZnO gel-like electrolyte in electrolytic Zn-Mn batteries results in superior discharge rate performance compared to the use of conventional aqueous electrolyte.Specifically, at a discharge current of 60 mA cm -2 , the discharge capacity is 0.44 and 0.32 mAh cm -2 when using ZnO gel-like electrolyte and conventional aqueous electrolyte, respectively.The experiment involved charging at a constant voltage of 2V vs. Zn/Zn 2+ to 0.5 mAh cm -2 and discharging to 0.8 V vs. Zn/Zn 2+ with a constant current density.The addition of ZnO has significantly improved the rate performance of the battery.Chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ for 30 min, discharge at 1 mA cm -2 to 0.8 V vs. Zn/Zn 2+ .
The basic oxide of Al2O3, MgO and CaO were as the electrolyte additive of electrolytic Zn-Mn batteries.As shown in Fig. S22A, B, although these different electrolytes all exhibited stable gel-like feature, the brown precipitate was observed in the MgO and CaO electrolyte.Obviously, the Mn(OH)2 or other manganese oxides were deposited in the MgO and CaO electrolyte, which may attributed to the excessively high pH levels of electrolyte (K θ sp of Mn(OH)2 is 4 × 10 -14 , the deposition pH is around 8).The insoluble substances in different electrolyte were collected, and the corresponding XRD patterns were shown in the Fig. S22C.Without obvious characteristic diffraction peaks of ZSH can be indexed in theses electrolyte.For the CaO gel-like electrolyte, the CaSO4‧2H2O was deposited.Subsequently, the chargedischarge capacities of these different gel-like electrolyte was recorded and shown in the Fig. S22D.The batteries with CaO and MgO gel-like electrolyte exhibit negligible charge capacity after 30 min chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ , which may attributed to the deposition of Mn(OH)2 and Other impurities in the electrolyte.For the Al2O3 gel-like electrolyte, the charge capacities are lower than the 1 M ZnSO4 +2 M MnSO4 electrolyte during the initial 20 cycles.We further prepared the Zn(OH)2 and Mg(OH)2 based gel-like electrolyte by using Zn(OH)2 and Mg(OH)2 as the additive in the 1 M ZnSO4 + 2 M MnSO4 electrolyte, and the concentration is 0.2g mL -1 .As shown in the Fig. S23A, the Color of Zn(OH)2 and Mg(OH)2 gel-like electrolyte is brown, which attributed to the deposition of Mn(OH)2 or other manganese oxides.the XRD pattern of insoluble substance of the Zn(OH)2 and Mg(OH)2 electrolyte were collected and shown in Fig. S23B.The characteristic diffraction peak of Zn4SO4(OH)6•5H2O (ZSH; PDF # 39-0688) can be detected in the Zn(OH)2 and Mg(OH)2 electrolyte.At the same time, the Mg(OH)2 phase also can be detected in the Mg(OH)2 electrolyte.
The electrochemical performance of Zn(OH)2 and Mg(OH)2 electrolyte were tested using the CR2032 button cell mold.During the initial 10 cycles, the charge capacity of Zn(OH)2 electrolyte is continually increased, and can reach 1.44 mAh cm -2 (it is higher than conventional aqueous electrolyte, but much lower than ZnO gel-like electrolyte).For the Mg(OH)2 electrolyte, after 30 min chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ , the charge capacity is negligible, which may attributed to the presence of insoluble Mg(OH)2 in the electrolyte.

Nano-Micro Letters S19/S28
According to the Figs.S22-S23, when selecting electrolyte additives, it is crucial to carefully evaluate their effect on the pH range of the electrolyte.Significant fluctuations in pH could lead to the formation of Mn(OH)2 or other manganese oxides precipitate, which can adversely impact the electrochemical performance of the batteries.Furthermore, the insoluble impurities in the electrolyte also can limit the electrochemical performance of batteries.To investigate the effect of ZnO electrolyte addition on the growth of Zn dendrites of Zn metal anode, the Zn//Zn symmetric cells were assembled using ZnO gel-like electrolyte and a CR2032 coin-type cell mold.As shown in Fig. S24A, in ZnO gel-like electrolyte, the plating/stripping performance of Zn//Zn symmetric cell exhibits a stable polarization voltage profile over 200h without obvious fluctuation at a current density of 1mA cm -2 with an area capacity of 1mAh cm -2 .In contrast, when using 1 M ZnSO4 +2 M MnSO4 solution as the electrolyte, the Zn//Zn cell exhibits a sudden reduction of the polarization voltage after cycling for 38 h at 1mA cm -2 , which ascribe to a dynamic dendrite-induced short circuit.After 10 plating/stripping process of 1mA cm -2 with 1mAh cm -2 , the surface of the metal zinc was observed by SEM.As shown in Fig. S24D, in conventional 1 M ZnSO4 +2 M MnSO4 electrolyte, the cliffy dendrite pieces and dark by-product aggregation on Zn foil were caught.Once switched to ZnO gel-like electrolyte., the surface of Zn metal became much smoother than the previous one (Fig. S24C).

Nano-Micro Letters S20/S28
Based on the experimental results presented above, it can be unequivocally concluded that the ZnO gel-like electrolyte can suppress the growth of Zn dendrites.Through extensive research in the previous published works, we found that the ZSH is extensively utilized by many researchers as a protective coating for the metal Zn anode, Thus, according to the published references and our in-situ differential electrochemical mass spectrometry (DEMS) gas analysis (Fig. 2E), Figures S6 and S7, the improved cycling ability of Zn metal anode in ZnO gel-like electrolyte may mainly attributed to the following points; 1) the ZnO gel-like electrolyte can alleviate corrosion of zinc metal (decreased HER reactivity).
2) The ZSH on the anode side can form a protective layer on the surface of Zn metal anode.
3) The ZSH layer shows high electrochemical stability, mechanical robustness, and active edges, which can effectively suppress the electrolyte-introduced side reactions and dendrite growth [S5-S7].The symbol of ---represent that no related information was found in the reference.

Fig. S1
Fig. S1 Charge surface area capacity and discharge surface area capacity during of the button electrolytic Zn-Mn batteries during the initial 20 cycles in different conventional aqueous electrolyte.(A) the pH of electrolyte is 1, (B) the pH of electrolyte is 2. The constant voltage charging time is 30min, and the constant current discharge current is 0.5 mA cm -2

Fig. S4 FESEM S28 Fig. S5
Fig. S4 FESEM images of (A) ZnO powder, (B) the ZnO gel-like electrolyte after drying.XRD pattern of (C) ZnO powder and (D) the gel-like electrolyte after washing and drying

Fig. S7
Fig. S7 Gas production test of electrolytic Zn-Mn batteries.(A and B) Prepared soft packed batteries and gas measurement device respectively.(C) The volume of gas produced during the battery cycling process.Chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ to 0.5 mAh cm -2 and discharge at 2 mA cm -2

Fig. S8
Fig. S8 Amplifying XRD pattern of CNTs cathode at the full charged state when using ZnO gel-like electrolyte as the electrolyte of batteries

Figure S10
Figure S10 illustrated operando Raman spectra of the CNTs cathode during the charge-discharge process with ZnO gel-like electrolyte.Initially, no observable peaks were detected in the fresh CNTs.However, after the completion of charging, three distinct Raman bands appeared at 502, 572, and 676 cm −1 , which correspond to the V4 (Mn-O) stretching vibration mode, stretching vibration of V3(Mn-O) in the basal plane of [MnO6] sheets and symmetric stretching vibration of V2 (Mn-O) in MnO6.This observation suggests the formation of layered manganese oxides.Upon discharging,

Fig. S11
Fig. S11 Schematic illustrating the morphology and phase evolution of cathode of during the charging and discharging reactions

Fig. S16 (
Fig. S16 (A) Normalized Mn K-edge XANES spectra and (B) Corresponding EXAFS spectra in r-space of the CNTs cathode in ZnO gel-like electrolyte at discharge state of 1.3 V vs. Zn/Zn 2+ .(C) Normalized Zn K-edge XANES spectra and (D) EXAFS spectra in r-space of the CNTs cathode in conventional aqueous electrolyte and ZnO gel-like electrolyte (30 min chronoamperometric charge of 2 V vs. Zn/Zn 2+ and discharged to 1.3 V vs. Zn/Zn 2+ under 0.1mAh cm -2 )

Fig. S17 FT
Fig. S17 FT of the k 3 -weighted EXAFS spectrum and fit real components at of the (A) MnO2 standard, CNTs cathode after full charging in (B) conventional aqueous electrolyte and (C) ZnO gel-like electrolyte after 30 min chronoamperometric charge of 2 V vs. Zn/Zn 2+

Fig. S18
Fig. S18 Theoretical structures used to perform FEFF calculations during EXAFS fitting

Fig. S20 The
Fig. S20 The Digital image of ZnO-gel-like electrolyte with different with different amounts of ZnO.(A) upright and (B) upside down bottle.Charge capacities of button cell electrolytic Zn-Mn batteries during initial 20 cycles in ZnO gel-like electrolyte with different amount of ZnO addition.(C) chronoamperometric charge for 30 min under (A) 1.9 V vs. Zn/Zn 2+ and (D) 2.0 V vs. Zn/Zn 2+ .The discharge current is 1 mA cm -2 .

Fig. S22 (
Fig. S22 (A, B) The digital photos of as-prepared 1 M ZnSO4 + 2M MnSO4 electrolytes with ZnO, Al2O3, MgO and CaO as the additive.(C) The XRD pattern of insoluble substance of the Al2O3, MgO and CaO gel-like electrolyte.(D) The chargedischarge capacities of different electrolyte during the initial 20 cycles.Chronoamperometric charge under 2.0 V vs. Zn/Zn 2+ for 30 min, discharge at 1 mA cm -2 to 0.8 V vs. Zn/Zn 2+ .

Fig. S23 (
Fig. S23 (A) the digital image of papered ZnO-based, Zn(OH)2-based and Mg(OH)2based electrolyte.(B) The XRD patterns of insoluble substance in the Zn(OH)2 and Mg(OH)2.(C) Charge and discharge capacities of different button cell electrolyte Zn-Mn batteries during the initial 20 cycles, the chronoamperometric charge of 2.0 V vs. Zn/Zn 2+ is 30 min, and the discharge current is 1 mA cm -2

Fig. S24 (
Fig. S24 (A) Comparison of the cycling stability of Zn-Zn symmetric cell in ZnO gellike electrolyte and 1 M ZnSO4 + 2M MnSO4 electrolyte (B) the XRD patterns of the Zn metal after 10 plating/stripping process.SEM images of the Zn metal after 10 after 10 plating/stripping process in (C)ZnO gel-like electrolyte and (D) conventional aqueous electrolyte.the current density is 1 mA cm −2 , and the capacity is 1 mA h cm −2

Table S2
The deposition mass of cathode after chronoamperometric charge of 2V vs. Zn/Zn 2+ in different electrolytes

Table S3
Structural parameters of the sample obtained from the XAFS fitting

Table S4
Summary of the parameters and electrochemical performance of aqueous electrolytic Zn-Mn batteries.

Table S5
Summary comparison of electrochemical performance of Zn-based energy storage systems based on the mass of active material in cathode